Packages for power transistors need to be thermally efficient and provide means for transferring heat produced by the transistor away from the transistor to keep it environmentally within its normal temperature operating range. Packages for power devices have consisted of metal bases where the backside of the device is mounted directly to the metal base which forms one contact to the semiconductor device. Other packages have a layer of insulating material or insulative adhesive between the device chip and the mounting base which may serve also as a heat sink to transfer heated generated by the device away from the device. Such packages may provide thermal transfer characteristics required by the device, but may not provide the capability of carrying high currents. In high density circuits of the present technology, it is necessary to have a device package for power semiconductor devices that can handle high currents and be thermally and electrically efficient.